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Abstract:

A method is provided for transmitting a control channel for resource
allocation to a terminal by a base station in an Orthogonal Frequency
Division Multiple Access (OFDMA) wireless communication system. An
additional resource allocation indicator is set indicating whether the
number of consecutive resource block sets allocated to a terminal is
greater than one. A reference control channel is generated including
reference resource allocation information for a first consecutive
resource block set and the set additional resource allocation indicator.
An additional control channel using additional resource allocation
information is generated, when there are one or more additional
consecutive resource block sets. At least one of the generated reference
control channel and the generated additional control channels is encoded
before transmission.

Claims:

1. A method for transmitting a control channel for resource allocation to
a terminal by a base station in an Orthogonal Frequency Division Multiple
Access (OFDMA) wireless communication system, the method comprising the
steps of:setting an additional resource allocation indicator indicating
whether a number of consecutive resource block sets allocated to a
terminal is greater than one;generating a reference control channel
including reference resource allocation information for a first
consecutive resource block set and the set additional resource allocation
indicator;generating an additional control channel using additional
resource allocation information, when there are one or more additional
consecutive resource block sets; andencoding at least one of the
generated reference control channel and the additional control channel
before transmission.

2. The method of claim 1, wherein the additional resource allocation
indicator comprises one bit to indicate presence or absence of the
additional control channel.

3. The method of claim 1, wherein the additional resource allocation
indicator comprises a plurality of bits to indicate presence or absence
of the additional control channel, and a number of consecutive resource
block sets included in the additional control channel.

4. The method of claim 1, wherein a number of bits required for indicating
a start point of an additional resource block included in the additional
resource allocation information is calculated using a number of resource
blocks following a block to which a reference resource block is
allocated.

5. A method for receiving a control channel for resource allocation
transmitted from a base station by a terminal in an Orthogonal Frequency
Division Multiple Access (OFDMA) wireless communication system, the
method comprising the steps of:checking a first consecutive resource
block set using reference resource allocation information included in a
reference control channel received from a base station;determining
whether a value of an additional resource allocation indicator indicates
that a number of consecutive resource block sets is greater than one;
andreceiving an additional control channel and checking one or more
additional resource blocks depending thereon, when the number of
consecutive resource block sets is greater than one.

6. The method of claim 5, wherein the additional resource allocation
indicator comprises one bit to indicate presence or absence of the
additional control channel.

7. The method of claim 5, wherein the additional resource allocation
indicator comprises multiple bits to indicate presence or absence of the
additional control channel, and a number of consecutive resource block
sets included in the additional control channel.

8. The method of claim 5, wherein a number of bits required for indicating
a start point of an additional resource block included in additional
resource allocation information is calculated using a number of resource
blocks following a block to which a reference resource block is
allocated.

9. A base station apparatus for transmitting a control channel for
resource allocation to a terminal in an Orthogonal Frequency Division
Multiple Access (OFDMA) wireless communication system, the apparatus
comprising:a scheduler for allocating resources for at least one
terminal, dividing the resources into reference allocation resources
corresponding to a first consecutive resource set and additional
allocation resources, and outputting the scheduling result and other
control information together with the resource allocation information;a
resource allocation controller for determining whether a number of
consecutive resource block sets is greater than one, based on the
received scheduling result, and generating an additional resource
allocation indicator corresponding to the determination result;a
multiplexer for multiplexing the reference allocation resources, other
control information, and additional resource allocation indicator;a first
encoder for encoding information output from the multiplexer to generate
a reference control channel; anda second encoder for encoding additional
allocation resources according to the determination result output from
the resource allocation controller, to generate an additional control
channel.

10. The apparatus of claim 9, wherein the additional resource allocation
indicator comprises one bit to indicate presence or absence of the
additional control channel.

11. The apparatus of claim 9, wherein the additional resource allocation
indicator comprises multiple bits to indicate presence or absence of the
additional control channel, and a number of consecutive resource block
sets included in the additional control channel.

12. The apparatus of claim 9, wherein a number of bits required for
indicating a start point of an additional resource block included in
additional resource allocation information is calculated using a number
of resource blocks following a block to which a reference resource block
is allocated.

13. A terminal apparatus for receiving a control channel for resource
allocation transmitted from a base station in an Orthogonal Frequency
Division Multiple Access (OFDMA) wireless communication system, the
apparatus comprising:a reference control channel checker for receiving a
reference control channel, and outputting check information of an
allocated reference resource block together with an additional resource
allocation indicator;an additional control channel checker for receiving
an additional control channel, and outputting check information of an
allocated additional resource block;an additional resource controller for
determining whether a number of consecutive resource block sets is
greater than one based on the additional resource allocation indicator,
and outputting a control signal according to the determination result;a
demultiplexer for inputting a signal received from the base station to
the reference control channel checker, separating an additional control
channel according to the control signal from the additional resource
controller, and outputting the separated additional control channel to
the additional resource controller; anda controller for controlling
reception of a physical channel according to the received reference
resource block check information and additional resource block check
information.

14. The apparatus of claim 13, wherein the additional resource allocation
indicator comprises one bit to indicate presence or absence of the
additional control channel.

15. The apparatus of claim 13, wherein the additional resource allocation
indicator comprises a plurality of bits to indicate presence or absence
of the additional control channel, and a number of consecutive resource
block sets included in the additional control channel.

16. The apparatus of claim 13, wherein a number of bits required for
indicating a start point of an additional resource block included in
additional resource allocation information is calculated using a number
of resource blocks following a block to which a reference resource block
is allocated.

Description:

PRIORITY

[0001]This application claims priority under 35 U.S.C. § 119(a) to a
Korean Patent Application filed in the Korean Intellectual Property
Office on Jun. 26, 2007 and assigned Serial No. 2007-63346, the
disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]The present invention relates generally to an apparatus and method
for allocating resources in a wireless communication system, and more
particularly, to an apparatus and method for allocating frequency
resources in an Orthogonal Frequency Division Multiple Access (OFDMA)
wireless communication system.

[0004]2. Description of the Related Art

[0005]Recently, in wireless communication systems, intensive research has
been conducted on Orthogonal Frequency Division Multiplexing (OFDM)
and/or OFDMA as a scheme suitable for high-speed data transmission in
wireless channels. OFDM, a scheme for transmitting data using multiple
carriers, is a kind of Multi-Carrier Modulation (MCM) that converts a
serial input symbol stream into parallel symbol streams, and modulates
each of them with multiple orthogonal subcarriers, i.e., multiple
orthogonal subcarrier channels before transmission.

[0006]FIG. 1 is a diagram illustrating a transmitter structure of a
general OFDM system.

[0007]An OFDM transmitter includes a channel encoder 101, a modulator 102,
a Serial-to-Parallel (S/P) converter 103, an Inverse Fast Fourier
Transform (IFFT) unit 104, a Parallel-to-Serial (P/S) converter 105 and a
Cyclic Prefix (CP) inserter 106. The channel encoder 101, also known as a
channel-encoding block, performs channel coding on an input information
bit stream. Generally, a convolutional encoder, turbo encoder, a Low
Density Parity Check (LDPC) encoder, etc. are used as the channel encoder
101. The modulator 102 generates modulation symbols by performing
modulation, such as Quadrature Phase Shift Keying (QPSK), 8-ary Phase
Shift Keying (8PSK), 16-ary Quadrature Amplitude Modulation (16-QAM),
64-QAM, 256-QAM, etc., on the output of the channel encoder 101. Although
not illustrated in FIG. 1, a rate-matching block for performing
repetition and puncturing can be further interposed between the channel
encoder 101 and the modulator 102. The S/P converter 103 serves to
convert the output of the modulator 102 into parallel data.

[0008]The IFFT unit 104 performs IFFT calculation on the output of the S/P
converter 103. The output of the IFFT unit 104 is converted into serial
data by the P/S converter 105. A CP inserter 106 inserts a CP code into
the output of the P/S converter 105. The Long Term Evolution (LTE) system
now under discussion as the next generation wireless communication system
of the Universal Mobile Telecommunication Service (UMTS) system in the
3rd Generation Partnership Project (3GPP) standard group for
asynchronous communication, uses Single Carrier Frequency Division
Multiple Access (SC-FDMA) for the uplink to solve the increase in
Peak-to-Average Power Ratio (PAPR), which is a defect of the OFDMA
scheme. SC-FDMA, a kind of the OFDM scheme, can be realized by adding a
Fast Fourier Transform (FFT) unit in front of the IFFT unit 104, and
precoding the data before it undergoes IFFT calculation in the IFFT unit
104.

[0009]FIG. 2 schematically illustrates resources of a general OFDM system.

[0010]As shown in FIG. 2, in OFDM or SC-FDMA, wireless resources are
expressed in a two-dimensional arrangement in time and frequency domains.
In FIG. 2, the horizontal axis represents a time domain 201, and the
vertical axis represents a frequency domain 202. In the time domain 201,
7 OFDM symbols constitute one 204, and two slots constitute one subframe
205. Generally, one subframe 205 has the same length as a Transmission
Time Interval (TTI), which is a basic transmission unit.

[0011]FIG. 3 is a diagram illustrating a data transmission/reception
procedure between a base station and a terminal in a general OFDM system.

[0012]In step 303, a terminal (or User Equipment (UE)) 320 generates a
Channel Quality Indicator (CQI) indicating the downlink channel condition
by measuring a Reference Signal (RS) such as a pilot, transmitted by a
base station (or Node B) 310. In step 304, the terminal 320 transmits the
CQI to the base station 310. In this case, the terminal 320 can transmit
a Channel Sounding Reference Signal (CS/RS) along with the CQI so that
the base station 310 can detect the uplink channel condition. Upon
receipt of the CQI and/or CS/RS, the base station 310 performs scheduling
in step 305, to determine downlink or uplink resources it will allocate
to the terminal 320. In step 306, the base station 310 transmits a
scheduling grant indicating the determined downlink/uplink resources to
the terminal 320. Then the terminal 320 checks in step 307 whether the
scheduling grant is delivered to the terminal 320 itself. If it is
checked in step 307 that the scheduling grant is transmitted to the
terminal 320 itself, the terminal 320 detects, in step 308,
downlink/uplink resources indicated by the scheduling grant and performs
data exchange with the base station 310 using the allocated
downlink/uplink resources.

[0013]In the scheduling process, the base station 310 delivers the
information necessary for data transmission/reception to the terminal 320
using a scheduling grant, and the scheduling grant is transmitted to the
terminal 320 over a forward Physical Downlink Control Channel (PDCCH).
The PDCCH uses some of the resources shown in FIG. 2. The base station
310 selects one or multiple PDCCHs from among available PDCCHs, and
transmits the scheduling grant to the terminal 320 through the selected
PDCCH(s).

[0014]The scheduling grant includes therein several types of information,
and its typical information can include the amount of packet information,
a modulation method, allocated resources, and Hybrid Automatic Repeat
reQuest (HARQ) information. Of the above-stated information, the
information on the allocated resources can have an important meaning in
the OFDMA communication system. In the OFDMA communication system, a
frequency band can be divided into a part having a good channel response
and a part having a bad channel response at an arbitrary time. Allocating
resources in the good channel response frequency band to the terminal is
required to increase the performance of frequency-selective scheduling.
Therefore, there is a need for a resource allocation method capable of
maximally increasing the performance of the frequency-selective
scheduling.

[0015]FIG. 4 is a diagram illustrating a frequency resource allocation
method in a general OFDM system.

[0016]The frequency resource allocation method of FIG. 4 illustrates a
start point of a resource block set and the number of resource blocks. In
FIG. 4, an entire frequency bandwidth 401 is composed of N Resource
Blocks (RBs), and when there is a wish to allocate a resource block #6
402 through a resource block #9 403 to an arbitrary terminal, the
resource allocation information included in a scheduling grant includes a
start point 404 (i.e., resource block #6 402) of the allocated resources
and a number of the allocated resource blocks 405.

[0017]FIG. 5 is a diagram illustrating frequency resources allocated in a
general OFDM system.

[0018]FIG. 5 shows several cases for a set of frequency resource blocks
allocated to an arbitrary terminal. Reference numeral 501 represents a
case where one consecutive resource block set is allocated to one
terminal. Reference numeral 502 represents a case where multiple
consecutive resource block sets are allocated to one terminal. Reference
numeral 503 represents a case where the entire resource block is
allocated to one terminal. In the cases 501 and 503, the resource
allocation method of FIG. 4 can perform resource allocation with one
start point and the number of resource blocks. However, in the case 502
where there is an intention to allocate resource block sets 511, 512 and
513 to one terminal, since multiple consecutive resource block sets are
available for resource allocation, it is necessary to indicate the start
point and the number of resource blocks separately for each of the
consecutive resource block sets.

[0019]In order to increase frequency-selective scheduling performance of
the OFDMA communication system, consideration should be given to the case
502 where multiple consecutive resource block sets are available.
However, in providing information on the start point of the resource
block sets and the number of resource blocks for resource allocation, as
the amount of information that should be signaled varies according to the
number of consecutive resource block sets, there are several formats for
scheduling grant channels transmitted to the terminal. When there are
several formats for scheduling grant channels, since the terminal cannot
judge whether a corresponding scheduling grant channel is a channel
transmitted to the terminal itself unless it decodes all the channels in
the several formats, its reception complexity increases with the number
of formats of the scheduling grant channels. In addition, the base
station should transmit many scheduling grant channels, causing a
reduction in efficient utilization of resources.

SUMMARY OF THE INVENTION

[0020]The present invention has been made to address at least the above
problems and/or disadvantages and to provide at least the advantages
described below. Accordingly, an aspect of the present invention provides
a resource allocation apparatus and method capable of increasing resource
efficiency in an OFDM and/or OFDMA-based wireless communication system.

[0021]Another aspect of the present invention provides a resource
allocation apparatus and method capable of reducing complexity of a
terminal in an OFDM and/or OFDMA-based wireless communication system.

[0023]According to one aspect of the present invention, a method is
provided for transmitting a control channel for resource allocation to a
terminal by a base station in an OFDMA wireless communication system. An
additional resource allocation indicator is set indicating whether the
number of consecutive resource block sets allocated to a terminal is
greater than one. A reference control channel is generated including
reference resource allocation information for a first consecutive
resource block set and the set additional resource allocation indicator.
An additional control channel using additional resource allocation
information is generated, when there are one or more additional
consecutive resource block sets. At least one of the generated reference
control channel and the generated additional control channel is encoded
before transmission.

[0024]According to another aspect of the present invention, a method is
provided for receiving a control channel for resource allocation
transmitted from a base station by a terminal in an OFDMA wireless
communication system. A first consecutive resource block set is checked
using reference resource allocation information included in a reference
control channel received from a base station. It is determined whether a
value of the additional resource allocation indicator indicates that the
number of consecutive resource block sets is greater than one. An
additional control channel is received and an additional resource block
depending thereon is checked, when the number of consecutive resource
block sets is greater than one.

[0025]According to a further aspect of the present invention, a base
station apparatus is provided for transmitting a control channel for
resource allocation to a terminal in an OFDMA wireless communication
system. The transmission apparatus includes a scheduler for allocating
resources for at least one terminal, dividing the resources into
reference allocation resources corresponding to a first consecutive
resource set and additional allocation resources, and outputting the
scheduling result and other control information together with the
resource allocation information. The transmission apparatus also includes
a resource allocation controller for determining whether the number of
consecutive resource block sets is greater than one based on the received
scheduling result, and generating an additional resource allocation
indicator corresponding to the determination result. Additionally, the
transmission apparatus includes a multiplexer for multiplexing the input
reference allocation resources, other control information, and additional
resource allocation indicator. Further, the transmission apparatus
includes a first encoder for encoding information output from the
multiplexer to generate a reference control channel, and a second encoder
for encoding input additional allocation resources according to the
determination result output from the resource allocation controller, to
generate an additional control channel.

[0026]According to yet another aspect of the present invention, a
reception apparatus is provided for receiving a control channel for
resource allocation transmitted from a base station in an OFDMA wireless
communication system. The reception apparatus includes a reference
control channel checker for receiving a reference control channel, and
outputting check information of an allocated reference resource block
together with an additional resource allocation indicator. The reception
apparatus also includes an additional control channel checker for
receiving an additional control channel, and outputting check information
of an allocated additional resource block. The reception apparatus
further includes an additional resource controller for determining
whether the number of consecutive resource block sets is greater than one
based on the additional resource allocation indicator, and outputting a
control signal to the demultiplexer according to the determination
result.

[0027]Additionally, the reception apparatus includes a demultiplexer for
inputting a signal received from the base station to the reference
control channel checker, separating an additional control channel
according to the control signal from the additional resource controller,
and outputting the separated additional control channel to the additional
resource controller. The reception apparatus also includes a controller
for controlling reception of a physical channel according to the received
reference resource block check information and additional resource block
check information.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]The above and other aspects, features and advantages of the present
invention will become more apparent from the following detailed
description when taken in conjunction with the accompanying drawings in
which:

[0029]FIG. 1 is a diagram illustrating a transmitter structure of a
general OFDM system;

[0030]FIG. 2 is a diagram schematically illustrating resources of a
general OFDM system;

[0031]FIG. 3 is a diagram illustrating a data transmission/reception
procedure between a base station and a terminal in a general OFDM system;

[0032]FIG. 4 is a diagram illustrating a frequency resource allocation
method in a general OFDM system;

[0033]FIG. 5 is a diagram illustrating frequency resources allocated in a
general OFDM system;

[0034]FIG. 6 is a diagram illustrating a structure of control channels
used in an LTE system;

[0035]FIG. 7A is a diagram illustrating a structure of a control channel
used for resource allocation in an LTE system;

[0036]FIG. 7B is a diagram illustrating a control channel structure for
transmitting resource allocation information according to an embodiment
of the present invention;

[0037]FIG. 8 is a signal flow diagram illustrating a control channel
transmission method for resource allocation in a base station according
to an embodiment of the present invention;

[0038]FIG. 9 is a control flow diagram for transmitting/receiving packet
data depending on received resource allocation information in a terminal
according to an embodiment of the present invention;

[0039]FIG. 10 is an internal block diagram illustrating a structure of a
base station's transmitter according to an embodiment of the present
invention; and

[0040]FIG. 11 is an internal block diagram illustrating a terminal's
receiver according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041]Preferred embodiments of the present invention are described in
detail with reference to the accompanying drawings. Similar components
are designated by similar reference numerals although they are
illustrated in different drawings. Detailed descriptions of constructions
or processes known in the art may be omitted to avoid obscuring the
subject matter of the present invention.

[0042]Although a description of the present invention will be given herein
with reference to the LTE system, by way of example, the present
invention can be applied to other wireless communication systems to which
base station scheduling is applied, without separate modification.

[0043]The present invention provides a method in which a base station
efficiently delivers resource allocation information in delivering
control information for data transmission/reception to a terminal in a
wireless communication system. The method provided herein includes a
method for generating control channels including indication information
for the resources that the terminal should transmit/receive.

[0044]FIG. 6 is a diagram illustrating a structure of control channels
used in an LTE system.

[0045]In an entire frequency bandwidth 601, the minimum time unit of
resources is one slot 603 that includes 7 (or multiple) OFDM symbols, and
two slots constitute one subframe 602. The subframe 602 is the minimum
resource allocation unit, and its length is generally equal to a
Transmission Time Interval (TTI), which is a data transmission unit.
PDCCHs are mapped to several OFDM symbols 604 (hereinafter referred to as
a `control channel resource region`) situated in the foremost part among
the multiple OFDM symbols included in one subframe 602, Physical Downlink
Shared Channels (PDSCHs), on which packet data is carried, are mapped to
the remaining OFDM symbols 605.

[0046]PDCCHs for downlink/uplink transmission for multiple terminals exist
in the control channel resource region 604, and generation of each PDCCH
will be described below. Control Channel Elements (CCEs) in a specific
size are used to generate PDCCHs, and one PDCCH is composed of one or
multiple CCEs. A base station transmits control information to a terminal
having a good channel state using PDCCH composed of one CCE at a high
coding rate. A base station transmits the same-sized control information
to a terminal having a bad channel state using PDCCH composed of multiple
CCEs, so that even the terminal in the bad channel condition can stably
receive the control information over PDCCH.

[0047]For example, PDCCH candidates 607 are generated using CCE sets, each
of which is composed of one CCE 608, two CCEs 609, four CCEs 610, or
eight CCEs among the multiple CCEs 606 existing in the entire control
channel resource region 604. In the case where the total number of CCEs
is N, N PDCCH candidates are generated when 1 CCE is used for each PDCCH;
[N/2] PDCCH candidates are generated when 2 CCEs are used for each PDCCH;
[N/4] PDCCH candidates are generated when 4 CCEs are used for each PDCCH;
and [N/8] PDCCH candidates are generated when 8 CCEs are used for each
PDCCH. Here, the expression `[A]` indicates the maximum integer not
exceeding `A`.

[0048]In FIG. 6, PDCCHs 611 and 612 each are allocated to their associated
terminals using one CCE. PDCCH 613 is composed of two CCEs, and PDCCH 614
is generated using four CCEs. The PDCCHs 611, 612, 613 and 614 are mapped
together to the control channel resource region 604 as shown in step 615.

[0049]The control channel resource region 604, to which multiple PDCCHs
are mapped, uses first several OFDM symbols in one subframe. In this
case, the number of simultaneously used PDCCHs, or the number of
necessary CCEs, can vary every time the number of the currently available
terminals and the channel states of the terminals are taken into account.
A size of the control channel resource region 604 for PDCCHs varies as
shown by reference numeral 616. The LTE system can change the size 616 of
the control channel resource region 604 where PDCCHs are included, using
a Control Channel Format Indicator (CCFI), which is periodic information.

[0050]The PDCCHs include therein a size of transmission packet data,
antenna information, a modulation method, HARQ information, resource
allocation information, etc. Information excluding the resource
allocation information, i.e., the data size, the antenna information, the
modulation method and the HARQ information, will be referred to herein as
`other control information`. The other control information is always
maintained in its size. However, the resource allocation information, as
described above, varies in its required size according to the number of
consecutive resource block sets.

[0051]FIG. 7A is a diagram illustrating a structure of a control channel
used for resource allocation in an LTE system.

[0052]While the other control information indicated by reference numeral
701 is equal in size, the resource allocation information indicated by
reference numeral 702 varies from a smallest size 703 to a size including
variable information 704 according to the number of consecutive resource
block sets. That is, information can be additionally included according
to the number of consecutive resource block sets. Therefore, the change
in the size due to the variable information 704 changes the PDCCH format,
increasing the load that the terminal should perform decoding on all
possible combinations of the received control channel formats.

[0053]The present invention provides a channel structure that fixes, to
one, the number of PDCCH formats the terminal should preferentially
receive, so that it can satisfy even the case where the number of
consecutive resource block sets is greater than one (indicating the
multiple number of consecutive resource block sets), while reducing the
decoding load of the terminal.

[0054]FIG. 7B is a diagram of a control channel structure for transmitting
resource allocation information according to an embodiment of the present
invention.

[0055]In FIG. 7B, PDCCH transmitted to each terminal is divided into a
reference control channel 717 and an additional control channel 718. The
reference control channel 717 is a channel including other control
information 711 and first consecutive resource block set (hereinafter
referred to as `reference resource block`) information 712. In this case,
the presence/absence of the additional consecutive resource block set(s)
is indicated through an additional resource allocation indicator 713.
That is, the presence/absence of the additional control channel 718 is
determined according to the additional resource allocation indicator 713.
Although a size of the additional control channel 718 is variable
according to the number of additional consecutive resource block sets,
the terminal has no need to perform blind decoding using all control
channel formats as in FIG. 7A. The terminal performs blind decoding on
the reference control channel in the first determined format. Upon
success in the decoding of the reference control channel 717, the
terminal only needs to additionally perform blind decoding on the
additional control channel 718 within the limit indicated by the
reference control channel 717. This provides a decrease in the complexity
and load required for reception decoding.

[0056]The additional resource allocation indicator 713 included in the
reference control channel 717 can be generated in two possible
embodiments.

[0057]In a first embodiment, the additional resource allocation indicator
is composed of one bit to indicate only the presence/absence of the
additional control channel. That is, it indicates only the
presence/absence of multiple consecutive resource block sets allocated by
a scheduler.

[0058]In a second embodiment, the additional resource allocation indicator
is composed of multiple bits to indicate not only the presence/absence of
the additional control channel, but also the number of consecutive
resource block sets included in the additional control channel. For
example, when 2 bits are used as in Table 1, there are four possible
types of the information indicated by the additional resource allocation
indicator.

[0059]That is, the second embodiment defines the formats of the additional
control channel according to the additional resource allocation indicator
to thereby reduce the number of blind decoding processes that the
terminal needs for reception of the additional control channel. This
contributes to a decrease in the complexity and load of the terminal's
reception operation.

[0060]The size of the additional resource allocation information included
in the additional control channel of FIG. 7B may be determined according
to the resource allocation information included in the reference control
channel.

[0061]Referring back to FIG. 5, the reference control channel includes
therein a resource block set indicated by reference numeral 511, and the
additional control channel includes therein resource block sets indicated
by reference numeral 512 and reference numeral 513. In this case, the
number of bits required for expressing a start point in indicating the
first consecutive resource block set 511 is the number of bits with which
it is possible to express the number of resource blocks available in the
frequency band. That is, the number of bits required for indicating a
start point of the reference resource block can be defined as shown in
Equation (1).

[0063]In the 10-MHz system where 100 RBs are used, the number of bits
required for indicating a start point of a resource block is 7. However,
since the part where additional allocation resource blocks are allocated
is limited to the parts after the block where the reference resource
block is allocated, the number of bits required for indicating the start
point can be reduced. That is, if the parts where additional allocation
resource blocks can be allocated after reference resource block is
allocated are reduced to 50 RBs, 6 bits are enough to indicate the start
points for the additional allocation resource blocks. This can be
mathematically expressed as Equation (2).

[0064]An embodiment of the present invention includes changing a size of
(or the number of) the additional resource allocation information bits
according to the reference allocation resources. A decrease in the number
of additional allocation resource bits can contribute to a reduction in
the transmission power and an increase in the coverage in transmitting
the additional control channel. The method of changing the bit size can
be applied together not only to the start points for resource allocation,
but also to the resource block length.

[0065]With reference to FIGS. 8 and 9, a detailed description is provided
of a control channel transmission/reception method of a base station and
a terminal based on the foregoing control channel structure according to
an embodiment of the present invention.

[0066]FIG. 8 is a signal flow diagram illustrating a control channel
transmission method for resource allocation in a base station according
to an embodiment of the present invention.

[0067]Referring to FIG. 8, as the transmission operation begins, a base
station performs scheduling in step 802. Thereafter, in step 803, the
base station determines whether resource allocation for an arbitrary
terminal has been performed. If it is determined in step 803 that the
resource allocation is not performed, the base station terminates the
methodology of FIG. 8. However, if it is determined in step 803 that
resources are allocated to a particular terminal, the base station
proceeds to step 804 where it checks consecutive resource block sets, and
sets the first consecutive resource block set as a reference resource
block. Thereafter, in step 805, the base station determines whether there
is any additional consecutive resource block set(s). If it is determined
in step 805 that the number of consecutive resource block sets is greater
than one (indicating the multiple number of consecutive resource block
sets), i.e., if there is an additional consecutive resource block set(s),
the base station proceeds to step 806, and if there is no additional
consecutive resource block set, the base station proceeds to step 809.

[0068]In step 809, the base station sets an additional resource allocation
indicator to indicate that the number of consecutive resource block sets
is one, then proceeds to step 810 where it encodes a reference control
channel including the reference resource block information, the other
control information, and the additional resource allocation indicator
indicating the single number of the consecutive resource block sets.
Thereafter, in step 811, the base station transmits the generated
reference control channel, and then ends the transmission operation.

[0069]However, in step 806, the base station sets the additional resource
allocation indicator. In this case, the additional resource allocation
indicator, as described above, can be composed of 1 bit to indicate only
the presence/absence of additional resource blocks, or can be composed of
two or more bits to indicate not only the presence/absence of added
resource blocks, but also the number of added resource block sets.
Thereafter, in step 807, the base station encodes a reference control
channel including reference resource block information, other control
information, and additional resource allocation indicator indicating the
multiple number of the consecutive resource block sets.

[0070]Thereafter, in step 808, the base station encodes the additional
resource allocation information to generate an additional control
channel. A size of the additional resource allocation information can be
calculated using Equation (2) as described above. Thereafter, in step
811, the base station transmits the generated reference control channel
and additional control channel, and then ends the transmission operation.

[0071]FIG. 9 is a control flow diagram for transmitting/receiving packet
data depending on received resource allocation information in a terminal
according to an embodiment of the present invention.

[0072]As the reception operation begins, a terminal performs decoding on a
reference control channel and checks its Cyclic Redundancy Code (CRC) in
step 902. That is, in step 902, the terminal checks only the
presence/absence of the reference control channel received using only the
format of the reference control channel. In this case, the terminal
determines the presence/absence of an error in received information
through the CRC check. Thereafter, in step 903, the terminal determines
whether a scheduling grant is transmitted thereto. If it is determined in
step 903 that no reference control channel is transmitted to the terminal
itself, the terminal ends the methodology of FIG. 9.

[0073]However, if it is determined in step 903 that a reference control
channel has been transmitted to the terminal itself, the terminal
proceeds to step 904 where it checks reference resource blocks included
in the reference control channel. Thereafter, in step 905, the terminal
checks an additional resource allocation indicator. In step 906, the
terminal determines whether a value of the additional resource allocation
indicator indicates that the number of consecutive resource block sets is
greater than one (indicating the multiple number of consecutive resource
block sets), and proceeds to step 907 if the number of consecutive
resource block sets is greater than one, and otherwise, proceeds to step
909.

[0074]If it is determined in step 906 that information in the additional
resource allocation indicator indicates a single number of consecutive
resource block sets, the terminal proceeds to step 909 where it
receives/decodes the packet data using only the reference resource block,
and then ends the reception operation. However, if it is determined in
step 906 that the information in the additional resource allocation
indicator indicates the multiple number of consecutive resource block
sets, the terminal proceeds to step 907 where it detects an additional
control channel and receives/decodes the detected additional control
channel. Thereafter, in step 908, the terminal checks additional resource
block information included in the additional control channel, and then
proceeds to step 909 where it receives/decodes the packet data using the
reference resource block and additional resource block information, and
then ends the reception operation.

[0075]With reference to FIGS. 10 and 11, a description is provided of a
transceiver structure according to an embodiment of the present
invention.

[0076]FIG. 10 is an internal block diagram illustrating a key structure of
a base station's transmitter according to an embodiment of the present
invention.

[0077]A scheduler 1001 allocates resources for an arbitrary terminal, and
divides the resources into reference allocation resources 1002 and
additional allocation resources 1003 according to the consecutive
resource set. The reference allocation resources 1002 are applied to a
multiplexer 1007 together with other control information 1004 and
additional resource allocation indicator 1006 generated by the scheduler
1001. The multiplexer 1007 multiplexes the input information, and
provides its output to a first encoder 1008. Then the first encoder 1008
encodes the received information according to a predetermined scheme to
generate a reference control channel. The encoded symbols are input to a
channel mapper 1010 where it is mapped to a physical channel and then
transmitted to the terminal.

[0078]Further, the scheduler 1001 outputs the information set in the
additional resource allocation indicator 1006 to a resource allocation
controller 1005. Then the resource allocation controller 1005 generates
the additional resource allocation indicator 1006 indicating the
single/multiple number of consecutive resource block sets, and provides
its output to the multiplexer 1007. That is, the resource allocation
controller 1005 determines the presence/absence of additional consecutive
resource block set(s) according to the scheduling result of the scheduler
1001. If it is determined by the resource allocation controller 1005 that
the number of consecutive resource block sets is greater than one, the
additional allocation resources 1003 are input to a second encoder 1009.
Then the second encoder 1009 encodes the additional allocation resources
1003 using a predetermined scheme to generate an additional control
channel, and provides its output to the channel mapper 1010. Then the
channel mapper 1010 maps the additional control channel to a physical
channel along with the reference control channel, and then transmits it
to the terminal by means of a transmission unit 1012.

[0079]The additional control channel is mapped by the channel mapper 1010
according to a control signal 1011 controlled by the resource allocation
controller 1005. In generating the control signal 1011, if the reference
control channel is mapped to one CCE shown in FIG. 6, the additional
control channel is mapped to a CCE succeeding the CCE to which the
reference control channel is mapped. To keep its flexibility, the
additional control channel can also be mapped to any CCE regardless of
the CCE to which the reference control channel is mapped. The number of
CCEs to which the reference control channel is mapped can vary according
to the channel condition, and the number of CCEs, to which the additional
control channel is mapped, is also determined according thereto. In
addition, since the size of the additional control channel varies
according to the number of consecutive resource block sets included in
the additional allocation resources 1003, the number of CCEs to which the
additional control channel is mapped can also vary together.

[0080]FIG. 11 is an internal block diagram illustrating a terminal's
receiver according to an embodiment of the present invention.

[0081]A terminal demultiplexes a signal received through a reception unit
1101 by means of a demultiplexer 1102. The demultiplexed signal is
basically input to a reference control channel checker 1104. That is, the
demultiplexer 1102 preferentially detects a reference control channel
signal, and outputs it to the reference control channel checker 1104. The
reference control channel checker 1104 determines whether a reference
control channel has been received at the terminal. When the reference
control channel is received, the reference control channel checker 1104
outputs an additional resource allocation indicator included in the
reference control channel to an additional resource controller 1103. Then
the additional resource controller 1103 controls a demultiplexer 1102
according to a value of the additional resource allocation indicator
included in the reference control channel. That is, if the additional
resource allocation indicator indicates the inclusion of additional
resources, the additional resource controller 1103 controls the
demultiplexer 1102 to demultiplex the channel signal except for the
reference control channel, and to provide its output to an additional
control channel checker 1105. If the additional resource allocation
indicator indicates the single number of consecutive resource block sets,
the additional resource controller 1103 controls the demultiplexer 1102
to receive no additional control channel. However, if the additional
resource allocation indicator indicates multiple consecutive resource
block sets, the additional resource controller 1103 controls the
demultiplexer 1102 to receive the additional control channel, and the
additional control channel checker 1105 checks the additional allocation
resources. Thereafter, the information from the reference control channel
checker 1104 and the information from the additional control channel
checker 1105 are input to a controller 1106 where they are used for
receiving a physical channel.

[0082]In FIG. 11, the structure necessary for data transmission/reception
can follow the general structure, or any modified structure available,
the details of which would be obvious to those skilled in the art.

[0083]As is apparent from the foregoing description, the application of
the present invention can efficiently signal allocation resources in the
OFDMA communication system, thereby simplifying the reception operation
of the terminal, enabling flexible resource allocation, and facilitating
efficient utilization of resources.

[0084]While the invention has been shown and described with reference to
certain preferred embodiments thereof, it will be understood by those
skilled in the art that various changes in form and details may be made
therein without departing from the spirit and scope of the invention as
defined by the appended claims.